Liquid crystal device

ABSTRACT

In a liquid crystal panel in which pseudo dot inversion driving is performed, the occurrence of flicker or vertical and horizontal strings is prevented by preventing an alignment shift between individual layers during the fabrication of a TFT array from producing a difference between the respective abilities of thin-film TFTs to charge adjacent pixels ( 61, 62 ). For this purpose, the liquid crystal display panel is constructed such that two TFTs which are enclosed by two adjacent image signal lines ( 21, 22 ) and scan signal lines ( 3 ) and adjacent to each other along the signal lines ( 21, 22 ) have respective source electrodes ( 71, 72 ) adjacent to the different image signal lines ( 21, 22 ). The source electrodes ( 71, 72 ) and drain electrodes ( 81, 82 ) of the two TFTs connected to the adjacent pixels ( 61, 62 ) are alternately arranged such that variations caused by the alignment shift in the sizes and areas of overlapping portions between the individual layers of the TFTs are equal or the same.

TECHNICAL FIELD

[0001] The present invention relates to liquid crystal devices and, moreparticularly, to an improvement in the display characteristics and thelike of a liquid crystal display device for performing a pseudo dotinversion.

BACKGROUND ART

[0002] (General Background Art)

[0003] Active matrix liquid crystal display devices using thin-filmtransistors (hereinafter also referred to as TFTs) as switching elementsare used widely in various fields including notebook personal computers,large-sized monitors for desk-top personal computers, mobile dataterminals, the display panels of digital video cameras, and liquidcrystal televisions.

[0004] As conceptually shown in (1, 1) and (1, 2) of FIG. 1, a liquidcrystal display device changes a state in which liquid crystal molecules40 are oriented with impression of a specified voltage on electrodeslocated over and under a liquid crystal layer on a pixel-by-pixel basis,thereby changes the light transmittance of each of pixels, andresultantly displays an image. In the drawing, 90 and 91 denote therespective electrodes formed on upper and lower substrates, 93 denotes apolarizing plate, and 94 denotes a polarizing plate or a reflectingplate. If the impression of the voltage on the electrodes is forso-called dc driving in which the direction of an electric field isconstantly the same, i.e., either the upper or lower electrode is usedconstantly as a positive or negative electrode when the pixel is in thestate which allows (or does not allow) passage of light as shown in (1,1) and (1, 2), positive or negative impurity ions in a liquid crystallayer are attracted to the negative or positive electrode so that thedistribution of the electric field between the pixel electrodes and thecommon electrode changes. This makes it difficult to apply a properelectric field to the liquid crystal molecules and causes a problem indisplaying a clear image.

[0005] There are also cases where the liquid crystal material iselectrolyzed or degraded. The attraction of impurity ions 45 to theupper and lower electrodes is conceptually shown in (1, 2) of FIG. 1.

[0006] When the pixel is in the state which allows (or does not allow)passage of light as shown in (2, 1) and (2, 2) of FIG. 1, so-called acdriving is normally performed in which the direction of the electricfield and the direction in which the liquid crystal molecules arearranged are inverted at specified intervals, i.e., the polarities ofthe upper and lower electrodes are inverted at specified intervals. Anexample of a circuit for the pixel to be used for this purpose is shownin (3, 1) and (3, 2) of FIG. 1.

[0007] The simplest scheme of ac driving is so-called frame inversiondriving in which each of the pixels over the entire display surface whenit is in the state which allows (or does not allow) passage of light hasa positive upper electrode (and a negative lower electrode) in a givendisplay period and has a negative upper electrode in the subsequentdisplay period. In short, the frame inversion driving scheme appliessignals of the same polarity to each of the pixels over the entiredisplay surface and inverts the polarity on a per display period basis.

[0008] However, an actual liquid crystal panel is asymmetrical becauseof the TFTs provided as the switching elements therein so that displaybrightness slightly differs depending on the positive or negativepolarity of the impressed voltage. In the frame inversion driving schemein which the signal of the same polarity is written in each of thepixels over the entire display surface, therefore, the difference inbrightness between a frame in which a positive signal is applied and aframe in which a negative signal is applied is observed as flicker. Itis to be noted that the structure of the pixel, the motion of the liquidcrystal molecules, the circuit for inversion, or the like in the liquidcrystal device shown in FIG. 1 is strictly exemplary or conceptual andthere are other types of variations. However, the basic items of frameinversion driving, control of light transmission using the motion ortilt of the liquid crystal molecules responsive to the electric field,and the like are the same.

[0009] To eliminate flicker, there is a method in which pixels withreversed polarities are alternately arranged in two dimensions so thatbrightness is averaged. As examples of the method, there can be listedimage-signal-line inversion driving which changes the polarity on a perimage-signal-line basis, scan-signal-line inversion driving whichperforms polarity inversion on a per scan-signal-line basis, acombination of the image-signal-line inversion driving and thescan-signal-line inversion driving, and dot inversion driving whichinverts the polarity of an electric field applied to pixels adjoininglongitudinally and laterally in a screen on a per pixel basis.

[0010] Of the foregoing methods, the dot inversion driving has theadvantages of unobtrusive flicker and display with a uniform brightnessdistribution since the pixels of positive and negative polarities arearranged in a checkered pattern. However, the dot inversion driving hasthe disadvantages of increased power consumption and increased chargingload on a driving IC since the polarities are inverted in each of therows and columns and therefore a driving waveform presents an increasednumber of voltage inversions during the transfer of a signal voltage tothe driving IC and during the charging of the pixel with an imagesignal. To eliminate the disadvantages, Japanese Unexamined PatentPublication No. HEI 4-223428 discloses pseudo dot inversion drivingwhich provides dot inversion display as a polarity pattern on a screen,while performing the image-signal-line inversion driving and thescan-signal-line inversion driving in terms of electric signals. Thepseudo dot inversion driving aims at highly uniform display, similarlyto the dot inversion driving, but with a simpler driving waveform thanused by the dot inversion driving.

[0011] In (1) and (2) of FIG. 2 are shown two equivalent circuits for aliquid crystal display device, which are for performing pseudo dotinversion driving and disclosed in the foregoing publication. In each ofthe circuits, a TFT 1 is disposed in the vicinity of each of the pointsof intersection of a plurality of image signal lines 2 and intersectingscan signal lines 3 in such a manner that connection is provided betweenthe source and gate electrodes of the TFT 1. The drain electrode of theTFT 1 is connected to a liquid crystal layer 4 and to accumulatedcapacitance 5 in parallel with the liquid crystal layer 4.

[0012] In (1) of FIG. 2, the TFTs 1 of two longitudinally adjoiningpixels along the image signal lines 2 have respective source electrodesconnected to the different image signal lines 2. If the liquid crystalpanel is driven in the image-signal-line inversion scheme, thepolarities of voltages impressed on the individual pixels are invertedas shown in FIG. 3 so that dot inversion display is achieved.

[0013] On the other hand, (2) of FIG. 2 illustrates another method inwhich the TFTs 1 of laterally adjoining pixels along the scan signallines 3 have respective gate electrodes connected to the different scansignal lines 3. In the liquid crystal panel, the polarities of voltagesimpressed on the adjacent pixels are inverted by the scan-signal-lineinversion driving so that dot inversion display is achieved.

[0014] Thus, dot inversion display is achievable by performing theimage-signal-line inversion driving in the liquid crystal display panelin which the source electrodes of the adjoining TFTs in the regionenclosed by the adjacent two image signal lines are connected to thedifferent image signal lines or in the liquid crystal display panel inwhich the gate electrodes of the adjoining TFTs in the region enclosedby the adjacent two scan signal lines are connected to the differentimage signal lines.

[0015] In either case, the polarity of the voltage impressed on each ofthe pixels is inverted in the subsequent frame period such that an acvoltage is impressed on each of the pixels.

[0016] (Background Art Viewed from Problems to be Solved by theInvention)

[0017] During the fabrication of a liquid crystal display panel, layersincluding a metal film, a semiconductor layer, and an insulating layerare deposited (formed) a plurality of times and the total of five toeight photolithographic steps are normally performed after thedeposition of each layer or after the deposition of given materials soas to pattern the individual layers (the process of removing unwantedportions and regions of the layers composed of the deposited givenmaterials by dry etching or the like and leaving only the requiredportions), whereby TFTs, pixels, and the like are formed. When thephotolithographic steps are performed, alignment is effected between asubstrate and a photo mask. However, an alignment shift (misalignment)of about one micrometer to several micrometers does occur depending onconditions including the sizes of the substrate and the display surface.

[0018]FIGS. 4 and 5 are views for illustrating the influence of theshift in a conventional TFT. It is to be noted that the depiction of adistinct boundary between insulating and protective films may be omittedin the subsequent plan views. In the steps of fabricating a TFT, thesource and drain regions are typically formed by simultaneouslypattering metal in a single layer. For the sake of clarity, the drawingsshow an exemplary case where the source and drain electrodes are shiftedonly in a direction parallel to the scan signal lines. Problemsoccurring in the case of a shift in an orthogonal direction arenegligible, though they differ depending on the configuration and sizeof the gate electrode.

[0019] In each of FIGS. 4 and 5, each of the TFTs 1 is composed of: agate electrode 11; a source electrode 7, 71, or 72; a drain electrode 8,81, or 82; and a channel protective film 14 and formed in the vicinityof each of the points of intersection of the image signal lines 2 andthe scan signal lines 3. The gate electrodes 11 are connected to thescan signal lines and the source electrodes 12 are connected to theimage signal lines. The drain electrodes 8, 81, and 82 are connected tothe pixel electrodes 6. Although the relative sizes of the pixelelectrodes are larger, they are depicted narrower and smaller since theyare not directly relevant to the spirit of the invention.

[0020] A cross-sectional view of the portion of the TFT is shown in thelower part of FIG. 4. In the drawing, 9 denotes a substrate, 89 denotesa contact hole for the drain electrode, 79 denotes a contact hole forthe source electrode, and 141 denotes a gate insulating film. As can beclearly seen from the cross-sectional view, metal films 82 and 72forming the source and drain electrodes are opposed to the semiconductorlayer 15 with a channel protective film 142 interposed therebetween andcapacitances are formed at the overlapping portions (the hatched anddotted portions in the drawing) when viewed from above an upper surfaceorthogonal to the substrate surface.

[0021] In FIG. 5, an electrode area occupied by the overlapping portionbetween the channel protective film 14 and source electrode of the TFTis designated at Ss and an electrode area occupied by the overlappingportion between the channel protective film 14 and drain electrode ofthe TFT is designated at Sd. In the TFT shown in (1) of FIG. 5 which isfree from an alignment shift, Ss=Sd is satisfied. In the case where ashift occurs in the direction in which the overlapping region betweenthe source electrode 71 and the channel protective film 14 increases asin (2) of FIG. 5 (rightward in the drawing), Ss>Sd is satisfied. In thecase where a shift occurs in the direction in which the overlappingregion between the source electrode 72 and the channel protective film14 decreases as in (3) of FIG. 5 (leftward in the drawing), Ss<Sd issatisfied conversely. In short, an ability difference is producedbetween the TFTs depending on the direction of a shift.

[0022]FIG. 4 shows the case where the source and drain electrodes of theTFT structure for performing the pseudo dot inversion driving by theimage-signal-line inversion driving using the equivalent circuitconfiguration of (1) of FIG. 2 are displaced rightward relative to thescan signal lines.

[0023] In the structure shown in the drawing, the source electrodes ofthe longitudinally adjoining TFTs which are interposed between the twoimage signal lines are connected to the different image signal lines.Specifically, one TFT 101 of the two TFTs interposed between the twoadjacent image signal lines 21 and 22 has the source electrode 71connected to the image signal line 21 and the other TFT 102 has thesource electrode 72 connected to the image signal line 22 other than theimage signal line 21.

[0024] In the structure, the rightward displacement of the source anddrain electrodes increases the overlapping region between the sourceelectrode 71 and the channel protective film in the upper TFT 101, whileit decreases the overlapping region between the source electrode 72 andthe channel protective film in the lower TFT 102. Accordingly, Ss>Sd issatisfied in the TFT 101 connected to the image signal line 21, whileSs<Sd is conversely satisfied in the TFT 102 connected to the imagesignal line 22.

[0025] Thus, the capacitance between the source and gate electrodes ofthe TFT and the capacitance between the drain and gate electrodes of theTFT differ from one scan signal line to another due to an alignmentshift during the fabrication of the TFT. This causes a differencebetween the charging abilities of the adjacent pixels and non-uniformdisplay such as flicker or a vertical/horizontal string.

[0026] The occurrence of the foregoing problems is not limited to thechannel-protective-film bottom-gate thin film transistor. FIG. 6 showsthe case of a thin-film transistor of another type. In (1) of FIG. 6 isshown the case of a top-gate thin-film transistor. In (1) of FIG. 6, thedistance LSG between the gate electrode 11 and the source electrode 7 isdifferent from the distance LDG between the gate electrode 11 and thedrain electrode 8. In addition, the distance LSLDD between the LDDregion 151 and the contact hole 79 for the source electrode is alsodifferent from the distance LDLDD between the LDD region 151 and thecontact hole 89 for the drain electrode. Although the gate insulatingfilm 141 and the channel protective film 142 are formed in (1) of FIG.6, the latter may not be formed in some cases.

[0027] In (2) of FIG. 6 is shown a channel-etched bottom-gate thin-filmtransistor, in which the overlapping portion between the sourceelectrode 7 and the semiconductor layer 15 is larger than theoverlapping portion between the drain electrode 8 and the semiconductorlayer.

[0028] In (3) of FIG. 6 is shown the case of the channel-etchedbottom-gate thin-film transistor in which an alignment shift hasoccurred between the gate electrode 11 and the semiconductor layer 15.Although thin-film transistors other than the foregoing include one inwhich, e.g., the length of the gate electrode in the channel direction(width) is smaller than that of the semiconductor layer, the occurrenceof the foregoing problems cannot be circumvented in any type.

[0029] The occurrence of the problems is not limited to a thin-filmtransistor. Similar problems may also occur in a diode, which areillustrated by using FIG. 7. In (1) of FIG. 7 is shown a plan view ofone pixel in a liquid crystal display device using a diode. In thedrawing, 111 denotes a diode, 6 denotes a pixel electrode, 2 denotes acounter electrode, 3 denotes a first electrode, 60 denotes a metal layer(end portion) connected to the pixel electrode, and 14 and 15 denote aninsulating film and a semiconductor layer.

[0030] A driving method will be described for reference purposes. Inaccordance with the method, a scan signal for the diode is inputted to ascan line. The diode to which the ON signal has been inputted is turnedON and the pixel electrode 6 has the same potential as the ON voltagefor the diode. The difference between an image signal applied to animage signal time and the pixel potential is stored in a liquid crystallayer. The diode is turned OFF during the scanning of the subsequentscan line and the voltage impressed in the ON state is held, wherebydisplay and the like are effected.

[0031] If the end portion 60 of the pixel electrode is coveredcompletely with the first electrode 99 as shown in (2) of FIG. 7, analignment shift is irrelevant. In reality, however, the end portion 60is covered halfway as shown in (3) of FIG. 7, so that a variation occursin the capacitance of the portion encircled by the symbol ◯.

[0032] Accordingly, the development of technology has been desired whichallows thin-film transistors arranged over the entire surface of aliquid crystal display panel for particularly performing pseudo dotinversion driving to have equal charging abilities even if an alignmentshift occurs between the individual layers.

DISCLOSURE OF THE INVENTION

[0033] To solve the foregoing problems, the present invention hascontrived source and drain electrodes and marginal lines thereof whichextend along scan signal lines or image signal lines such thatoverlapping portions between the individual components of each of TFTswithin a liquid crystal panel do not vary when an alignment shift occursand Ss=α·Sd is constantly satisfied even under worst conditions. Inaddition, the present invention has also contrived placement andconfiguration.

[0034] Besides, the present invention has also effected an improvementin color display performance in pseudo dot conversion and the like.

[0035] Specifically, the following structures have been adopted.

[0036] In one aspect, the present invention is a liquid crystal devicehaving: a large number of image signal lines and a large number of scansignal lines provided on a glass substrate or panel in accordance withthe specifications or the like with spacings corresponding to pixel size(which is about 40 to 100 μm depending on pixel type, uses of thedevice, and the like), the width of a black matrix between pixels, andthe like; the pixels arranged in a so-called check pattern in a regionenclosed by the two types of signal lines; and a TFT (which may be adiode or the like in some cases) formed at any of upper, lower, left,and right corners of each of the pixels or in the vicinity thereof,wherein the semiconductor portion, source electrode, gate electrode, anddrain electrode of the TFT have marginal portions extending in the samedirection as the image signal lines or scan signal lines (in parallelwith one of the image and scan signal lines and orthogonal to theother). Each of the electrodes has an angular, especially rectangularconfiguration (including a square configuration. In some cases, it maybe an L-shaped or like configuration).

[0037] In addition, the positions and sizes of the semiconductorportion, the gate electrode, the drain electrode, and the sourceelectrode are determined such that, even if a mask alignment (placement)slightly shifts during the formation thereof especially byphotolithography, the overlapping portion between the gate electrode andthe semiconductor layer is invariable and at least one (preferably bothand basically both in practical use) of the overlapping portion betweenthe gate electrode and the drain electrode and the overlapping portionbetween the gate electrode and the source electrode is invariable whenviewed from above the substrate (the direction orthogonal to the displaysurface or the side from which the user views the display surface of theproduct).

[0038] When attention is focused on two TFTs which are (in principle)adjacent to each other in the longitudinal or lateral direction, even ifa variation occurs depending on the direction of an alignment shift, thevariation occurs equally in each of the overlapping portions between thegate electrode and the other two electrodes.

[0039] This allows automatic compensation for a capacitance variationcaused by an alignment shift in a normal range (about 2 to 3 μm and 6 μmin some cases depending on the sizes of the pixel, TFT, and the like)via a gate insulating film between the gate and drain electrodes, achannel protective film between the gate and source electrodes, or thelike.

[0040] Likewise, compensation is provided for a capacitance variationcaused by variations in the distance between the gate and drainelectrodes or between the gate and source electrodes, in the distancebetween the end of the portion of the semiconductor layer immediatelyunder the gate electrode or the end portion of the LDD region and thedrain or source electrode, and in the distance between contact holes forthe electrodes.

[0041] If the two TFTs that have been paired up compensate for analignment shift, consideration is also given to the longitudinal orlateral arrangement of the source (S) and drain (D) electrodes of theTFTs such that a pattern of SDSD or DSDS is achieved in the drawing. Itwill also be appreciated that, in this case, the types or models of theTFTs are not limited and any TFTs may be used whether they are ofbottom-gate type, channel-etched type, or top-gate type.

[0042] If attention is focused on one TFT in which the number of atleast one of the source and drain electrodes is plural, the plurality of(numerous in most cases and normally two for fabrication convenience)electrodes of the TFT include two located aside the respective ends inthe longitudinal or lateral direction of one of the other (smallernumber of) electrodes and the semiconductor portion of the TFT locatedabove or below the substrate have the ends located near the respectivecenter portions of the widths of the electrodes located aside the endsin the longitudinal direction. This provides compensation for variationsin the overlapping portion caused by an alignment shift.

[0043] If one TFT has a large number of source electrodes and a largenumber of drain electrodes, the source and drain electrodes arepreferably arranged such that they alternate longitudinally orlaterally.

[0044] The source or drain electrode is formed to have an L-shapedconfiguration such that the L-shaped portion fits in and overlaps thesemiconductor portion (layer) located above or below the substrate.

[0045] The position at which the TFT, in particular the gate electrodeportion, is formed is determined such that the area, aperture ratio, andbrightness of a pixel portion are improved.

[0046] Besides, compensation is also provided for an alignment shifteven with diodes by contriving the arrangement thereof and the like.

[0047] To retain excellent performance over an extended period, thepolarity of each pixel is inverted on a perpredetermined-number-of-display-periods basis, e.g., on a per displayperiod basis in terms of display characteristics. Likewise, the polarityis inverted on a per predetermined-number-of-signal-lines basis, e.g.,on a per scan (signal) line bases or on a per image (signal) line basis.In particular, so-called pseudo dot inversion is adopted in which thepixels corresponding to the positive and negative polarities arearranged longitudinally or laterally adjacent to each other and whichallows the use of a relatively simple circuit. In this case, thearrangement and placement of the TFTs, particularly the longitudinal orlateral juxtaposition of the source and drain electrodes of the pair ofTFTs and the connection thereof to the individual signal lines aredetermined such that compensation is provided for the alignment shiftdescribed above.

[0048] If the individual pixels in three primary colors for colordisplay are arranged in a so-called mosaic pattern in pseudo dotinversion, lines composed of positive pixels and lines composed ofnegative pixels are alternately arranged in oblique directions for eachof the colors, which may cause a problem when viewed from a professionalstandpoint. To prevent this, the positive and negative pixels arealternately arranged (in the longitudinal direction) in so-calledstripes in each of the primary colors. In the adjacent stripes in thesame color, the positive and negative pixels are shifted by one pixelposition (in the longitudinal direction), which provides color displaysuitable for professional use.

[0049] The present invention is also applicable to an extended use inequipment in which a liquid crystal is driven with a switching element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a view showing the application of an ac current in apixel and the advantage thereof;

[0051]FIG. 2 is an equivalent circuit diagram when a TFT is used todrive a conventional liquid crystal;

[0052]FIG. 3 is a view showing the polarities of charge in individualpixels in dot inversion driving;

[0053]FIG. 4 includes plan and cross-sectional views of a TFT as a priorart switching element for a pixel;

[0054]FIG. 5 is a view for illustrating an alignment shift;

[0055]FIG. 6 shows embodiments of an alignment shift in various (typesof) thin-film transistors;

[0056]FIG. 7 shows the occurrence of an alignment shift in a diode;

[0057]FIG. 8 is a view showing the arrangement of TFTs on a liquidcrystal panel according to a first embodiment of the present invention;

[0058]FIG. 9 is a plan view of a liquid crystal panel according to asecond embodiment of the present invention;

[0059]FIG. 10 is a plan view showing the arrangement of TFTs on a liquidcrystal panel according to a third embodiment of the present invention;

[0060]FIG. 11 is a plan view showing the arrangement of TFTs on a liquidcrystal panel according to a fourth embodiment of the present invention;

[0061]FIG. 12 is a plan view showing the arrangement of TFTs on a liquidcrystal panel according to a fifth embodiment of the present invention;

[0062]FIG. 13 shows the arrangement of TFTs on a liquid crystal panel ina transverse electric field mode as a sixth embodiment of the presentinvention;

[0063]FIG. 14 includes plan views of various liquid crystal panels eachusing a channel-etched TFT as a seventh embodiment of the presentinvention;

[0064]FIG. 15 is a view showing 1 of an eighth embodiment of the presentinvention;

[0065]FIG. 16 is a view showing 1 of the eighth embodiment;

[0066]FIG. 17 is a view showing 1 of the eighth embodiment;

[0067]FIG. 18 is a view showing 1 of the eighth embodiment;

[0068]FIG. 19 is a view showing 1 of the eighth embodiment;

[0069]FIG. 20 is a view showing 1 of the eighth embodiment;

[0070]FIG. 21 is a view showing 1 of a ninth embodiment of the presentinvention;

[0071]FIG. 22 is a circuit diagram of a liquid crystal display panelaccording to each of eleventh and twelfth embodiments of the presentinvention;

[0072]FIG. 23 is a view showing the impression of a voltage in theforegoing two embodiments;

[0073]FIG. 24 is a view conceptually showing the principle of theimpression of the voltage on a signal line in pseudo dot conversion;

[0074]FIG. 25 is a view showing technology according to a thirteenthembodiment of the present invention; and

[0075]FIG. 26 is a view showing an optical logic element as a fourteenthembodiment of the present invention.

Explanations of Letters or Numerals

[0076]1, 101, 102 . . . Thin-Film Transistors (TFTs)

[0077]111 . . . Diode

[0078]2, 21, 22 . . . Image Signal Lines

[0079]3, 31, 32 . . . Scan Signal Lines

[0080]40 . . . Liquid Crystal Molecule

[0081]4 . . . Liquid Crystal Layer

[0082]45 . . . Impurity Ion

[0083]5 . . . Accumulated Capacitance

[0084]6 . . . Pixel Electrode

[0085]60, 61, 62 . . . Pixel Electrodes

[0086]7, 71, 72 . . . Source Electrodes

[0087]8, 81, 82 . . . Drain Electrodes

[0088]11 . . . Gate Electrode

[0089]14 . . . Channel Protective Film

[0090]15 . . . Semiconductor Layer

[0091]9 . . . Substrate

[0092]90 . . . Upper Substrate (Upper Electrode)

[0093]91 . . . Lower Substrate (Lower Electrode)

[0094]92 . . . Counter Electrode

[0095]93 . . . Polarizing Plate

[0096]94 . . . Polarizing Plate, Reflecting Plate

BEST MODES FOR CARRYING OUT THE INVENTION

[0097] The present invention will be described based on the embodimentsthereof.

[0098] (Embodiment 1)

[0099] The present embodiment relates to an improvement in the planarrangement of two pixels adjoining along image signal lines on a liquidcrystal display panel for performing a pseudo dot inversion shown in (1)of FIG. 2.

[0100]FIG. 8 shows a principal portion of the present embodiment. In thedrawing, first and second bottom-gate TFTs 101 and 102 are formed in thevicinity of the points of intersection of first and second image signallines 21 and 22 and scan signal lines 3 intersecting the first andsecond image signal lines 21 and 22. The TFTs have respective gateelectrodes 11 connected to the scan signal lines 3, respective sourceelectrodes 71 and 72 connected to the image signal lines 21 and 22, andrespective drain electrodes 81 and 82 connected to pixel electrodes 61and 62. Each of the pixel electrodes holds a liquid crystal betweenitself and a common electrode formed on the counter substrate. Ingeneral, each of the pixel electrodes forms an accumulated capacitancebetween itself and the scan signal line or an additional accumulatedcapacitance line formed to compensate for a reduction in a write voltageon a liquid crystal layer during a voltage retention period caused by aleakage current in the TFT. However, the depiction of the accumulatedcapacitance and the accumulated capacitance line is omitted because ofits intricacy and obviousness.

[0101] The liquid crystal display panel is characterized in that thechannel direction connecting the source and drain electrodes of the TFTsserving as the switching elements is in orthogonal relation to the imagesignal lines 21 and 22. As a result, the drain and source electrodes 81and 71 of the TFT 101 and the drain and source electrodes 82 and 72 ofthe TFT 102 are alternately arranged along the image signal lines (fromtop to bottom) in FIG. 8.

[0102] Consideration will be given to the case where an alignment shiftoccurs in FIG. 8 and the source and drain electrodes of the two TFTs aredisplaced in parallel with the scan signal line 3. In this case, theareas Ss and Sd of the overlapping portions between the channelprotective film and the source electrode 71 or 72 and between thechannel protective film and the drain electrode 81 or 82 are invariablein each of the TFTs, which is different from the conventional TFT.Consequently, the ability to charge each of the pixels is no moredifferent from one scan signal line to another.

[0103] An alignment shift may also occur in a direction perpendicular tothe scan signal line but, in this case also, the ratio between the areasSs and Sd of the overlapping portion between the channel protective filmand the source electrode and between the channel protecting film and thedrain electrode is equal in each of the two TFTs.

[0104] Although the drain and source electrodes are arranged along theimage signal lines (from top to bottom) in FIG. 8, it will easily beunderstood that the drain and source electrodes may also be arranged inthe reverse order (SDSD). It will be appreciated that each of theelectrodes is not limited to a particular configuration and may have arectangular or like configuration in consideration of compensation fordisplacement, production, and the like provided that the electrode iscomposed of parallel portions whether it is slightly large in width orlength. It will also be appreciated that the pixel portion is equippedwith a black matrix, an alignment (orientation) film, a color filter, apolarizing plate, and the like if required, though they are not shownfor the prevention of intricacy because they have no direct relevance tothe spirit of the invention. The same shall apply to the otherembodiments which will be described later.

[0105] (Embodiment 2)

[0106] The present embodiment is characterized in that the source anddrain electrodes of the TFTs are arranged in succession along the scansignal lines.

[0107]FIG. 9 shows the present embodiment. The present embodiment alsoaims at a liquid crystal display panel using bottom-gate TFTs to performa pseudo dot inversion, similarly to the preceding embodiment shown inFIG. 8.

[0108] In contrast to the preceding embodiment in which the drain andsource electrodes 81 and 71 and the drain and source electrodes 82 and72 are alternately arranged along the image signal lines (from top tobottom in the drawing), the source and drain electrodes 71 and 81 andthe source and drain electrodes 72 and 82 are arranged in successionalong the scan signals (from left to right) in the present embodiment.

[0109]FIG. 4 shows the case where the source and drain electrodes of theTFTs are displaced in parallel with the scan signal line 3. Due to analignment shift, the TFTs have different electrode areas Ss and Sdoccupied by the overlapping portions between the channel protectivefilms 14 of the two TFTs and the source and drain electrodes thereofHowever, the two TFTs and all TFTs in the panel have equal variations inSs and Sd, which is different from the TFTs in the conventionalstructure. Consequently, the ability to charge each of the pixels is nomore different from one scan signal line to another.

[0110] It will be appreciated that an alignment shift perpendicular tothe scan signal lines exerts no influence on the structure shown in FIG.4.

[0111] Although the drain and source electrodes of the TFT in the lowerpart of the drawing have slightly irregular configurations in thepresent embodiment, they present no particular problem (in practicaluse). However, it will be understood that compensation may be providedfor the size of the pixel or the like.

[0112] (Embodiment 3)

[0113] The present embodiment is characterized in that the gateelectrodes of TFTs adjoining along the scan signal lines are connectedto the different scan signal lines.

[0114]FIG. 10 shows a liquid crystal display panel according to thepresent embodiment. The present embodiment also aims at a liquid crystaldisplay panel for performing pseudo dot inversion driving shown in (2)of FIG. 2. FIG. 10 shows two pixels adjoining along the scan signallines on the panel. Each of the first and second TFTs 101 and 102 has agate electrode 11, a source electrode, a drain electrode, and a channelprotective film 14. The depiction of the accumulated capacitances andthe accumulated capacitance lines is omitted.

[0115] The first TFT 101 has the source electrode 71 connected to thefirst image signal line 21, the gate electrode 11 connected to a firstscan line 31, and the drain electrode 81 connected to a pixel electrode6. The second TFT 102 has the source electrode 72 connected to thesecond image signal line 22, the gate electrode 14 connected to a secondscan signal line 32, and the drain electrode 82 connected to the pixelelectrode.

[0116] As a consequence, the source and drain electrode 71, 81, 72, and82 of the two TFTs are arranged in this order along the image signallines (from top to bottom) in FIG. 10.

[0117] In the structure also, charging abilities are no more differentfrom one TFT to another even if an alignment shift occurs between theindividual layers and excellent image display can be performed,similarly to the first embodiment.

[0118] (Embodiment 4)

[0119] The present embodiment is characterized in that the source anddrain electrodes of the TFTs are arranged in succession along the scansignal lines.

[0120]FIG. 11 shows the present embodiment. The present embodiment alsorelates to a liquid crystal display panel for performing pseudo dotinversion driving shown in (2) of FIG. 2, similarly to the precedingthird embodiment.

[0121] In contrast to the preceding embodiment shown in FIG. 10 in whichthe source and drain electrodes 71 and 81 and the source and drainelectrodes 72 and 82 are arranged in this order from top to bottom alongthe image signal lines, the source and drain electrodes 71 and 81 andthe source electrode and drain electrodes 72 and 82 are arranged in thisorder from left to right along the scan signal lines in the presentembodiment shown in FIG. 11.

[0122] In the structure also, charging abilities are no more differentfrom one TFT to another even if an alignment shift occurs between theindividual layers and excellent image display can be performed for thesame reasons as described in the first embodiment.

[0123] (Embodiment 5)

[0124] The present embodiment forms TFTs on the scan signal lines.

[0125]FIG. 12 shows the present embodiment. The TFT 1 formed within thepixel in the first embodiment shown in FIG. 8 (FIG. 1) is placed outsidethe scan signal line 3. Even if a TFT is formed on a scan line as in thepresent embodiment, the source and drain electrodes of the TFT can bearranged along the image signal lines in the order as shown in the firstembodiment. This achieves the same effects as described in the firstembodiment. The arrangement also allows the designing of a pixel havinga large area and bright display by increasing the aperture ratio of theliquid crystal display panel.

[0126] It is also possible to place the TFT on the scan signal line inthe other embodiments. Even if the placement is applied to the otherembodiments, the charging abilities of the TFTs have no differencetherebetween irrespective of an alignment shift and uniform display canbe performed. In addition, the increased aperture ratio provides brightdisplay.

[0127] (Embodiment 6)

[0128] The present embodiment relates to a liquid crystal panel in atransverse electric field mode.

[0129] Each of the foregoing embodiment has described the case where thepixel electrodes and the common electrode opposed to the pixelelectrodes are formed on the different substrates. However, the sameeffects are achievable with a liquid crystal display panel in atransverse electric field mode such as an IPS (In-Plane Switching) modein which the pixel electrodes and the common electrode are formed on asingle substrate as shown in FIG. 11, in an FFS mode, or in an HS mode.

[0130] The present embodiment will be described briefly with referenceto FIG. 13. In FIG. 13 is shown a view obtained by viewing the liquidcrystal panel from above. The source electrodes 71 and 72 of the TFTs101 and 102 of the upper and lower two electrodes are connected to theadjacent image signal lines 71 and 72, similarly to FIG. 7. In thedrawing, 92 denotes a common electrode formed on a single (opposite tothe user side and lower) substrate and 6 denotes each of pixelelectrodes which are connected to the drain electrode 81 and 82 of theTFTs 101 and 102.

[0131] As for the description of the principle and mechanism of a liquidcrystal in the transverse electric field mode, FFS mode, HS mode, or thelike, the description thereof is omitted since it is so-calledwell-known technology.

[0132] (Embodiment 7)

[0133] The present embodiment uses channel-etched TFTs.

[0134] Although each of the foregoing embodiments has described the caseof using the channel-protected TFTs, the present invention is notlimited thereto. The channel-etched TFTs may also be used in the FFS,HS, or other mode. In (1) to (5) of FIG. 14. are shown cases where thechannel-etched TFTs are used. Those shown in (1) to (5) of FIG. 14correspond to FIGS. 6 to 10 and have the semiconductor layer 15patterned instead of using the channel protective film.

[0135] In the arrangement of the TFTs of the present invention also, theareas occupied by the overlapping portions between the semiconductorlayers 15 and the source and drain electrodes 71, 72, 81, and 82 are nomore different from one pixel to another even in the case of using thechannel-etched TFTs, similarly to the case of using thechannel-protected TFTs. This allows excellent image display.

[0136] (Embodiment 8)

[0137] The present embodiment relates to so-called U-shaped TFTs in eachof which the number of at least one of the source and drain electrodesis plural.

[0138] In FIGS. 15 to 20 are shown the arrangements of image signallines, pixel signal lines, and the source, drain, and gate electrodes ofadjacent two TFTs of the present embodiment which are paired up in thelongitudinal or lateral directions or the overlapping relations amongportions related to the capacitances of the TFTs when viewed from abovethe substrate.

[0139] In FIG. 15, the two TFTs arranged laterally between the adjacenttwo image signal lines have source electrodes connected to the differentimage signal lines. In FIG. 16, the two TFTs arranged longitudinallybetween the adjacent two scan signal lines have gate electrodesconnected to the different scan signal lines. Each of the TFTs shown inFIG. 15 which have the respective source electrodes connected to thedifferent scan signal lines between the adjacent two image signals linesis provided with two source electrodes 7. Each of the TFTs shown in FIG.16 which have the respective gate electrodes connected to the differentscan signal lines between the adjacent two scan signal lines is providedwith two source electrodes 7. The two electrodes 7 have the drainelectrode 8 interposed midway therebetween. As a result, it is no morenecessary to select between landscape and portrait orientations.

[0140] It will be appreciated that, in each of FIGS. 15 and 16, thenumber of the source electrodes and that of the drain electrodes areinterchangeable and the positional relationship between the source anddrain electrodes is reversible. Although 15 denotes the semiconductorlayer of the channel-etched TFT in FIG. 16 and the like, 15 denotes achannel protective film if a channel-protected TFT is used instead.

[0141] In each of FIGS. 17 to 20, two source electrodes and two drainelectrodes are provided and arranged equidistantly in the lateral orlongitudinal direction. The semiconductor layer or the overlyinginsulating film 14 is configured as an elongated square so that theareas of overlapping portions with the source and drain electrodes donot change even if a slight alignment shift occurs in the direction ofthe shorter sides (lateral direction) of the semiconductor layer or theinsulating film 14. The shorter side portions of the semiconductor layeror the insulating film 14 in the longitudinal or lateral directionextend to a region near the center portions of the source or drainelectrodes which are also elongated in the lateral or longitudinaldirection so that the characteristics of the two TFTs do not vary orvary equally even if a slight alignment shift occurs in the direction ofthe longer sides (longitudinal direction).

[0142] Although one TFT has two source electrodes and two drainelectrodes at the maximum in the present embodiment, it will beunderstood that a larger number of source and drain electrodes may alsobe provided. In this case, it will also be understood that the sourceand drain electrodes need not necessarily be arranged equidistantly oralternately except for the electrodes at the ends.

[0143] In FIGS. 17 and 18, the respective source electrodes of the twoTFTs arranged laterally are connected to the different source lines. InFIGS. 19 and 20, the respective gate electrodes of the two TFTs arrangedlongitudinally are connected to different gate lines. However, thedescription of the arrangements will be omitted for the prevention ofredundancy.

[0144] (Embodiment 9).

[0145] The present embodiment will describe the case where each of theTFTs has an L-shaped configuration.

[0146]FIG. 21 shows several examples of the arrangement of a pair ofTFTs arranged longitudinally or laterally according to the presentembodiment. As can be seen from the drawing, each of the two TFTsarranged longitudinally or laterally has an L-shaped drain electrode 8and the source electrodes thereof are connected to the different andadjacent image signal lines in the present embodiment. A semiconductorlayer 14 having a rectangular plan configuration completely overlaps theL-shaped portion of the drain electrode 8 and the source electrode 7.

[0147] In (1) of FIG. 21 is shown the case where the two TFTs arearranged laterally. In (2) of FIG. 21 is shown the case where the twoTFTs are arranged longitudinally. In (3) of FIG. 21 is shown the casewhere the TFTs are formed on the gates. In any of (1), (2), and (3) ofFIG. 21, the areas of the encircled portions which ought to have beenrelated to capacitance conventionally or the overlapping areas of theencircled portions are constant irrespective of an alignment shift.

[0148] (Embodiment 10)

[0149] The present embodiment relates to diodes.

[0150] The present embodiment is shown in (2) of FIG. 22.

[0151] For the reasons described above, an alignment shift produces acapacitance difference between the diodes in the arrangement of the TFTsshown in (1) of FIG. 22. However, the arrangement of the TFTs as shownin (2) of FIG. 22 has higher resistance to an alignment shift since thecapacitances of the diodes are irrelevant to a longitudinal shift andchange equally in response to a lateral shift.

[0152] (Embodiment 11)

[0153] The present embodiment relates to a method for driving each ofthe liquid crystal display panels described in the first and secondembodiments.

[0154] In (1) and (2) of FIG. 23 is shown a circuit of the presentembodiment. By inverting the polarities of image signal voltagesimpressed on the image signal lines 2 arranged on the liquid crystaldisplay panel such that the positive and negative polarities alternatealong scan signal lines 3 as shown in (1) of FIG. 23, the voltages ofdifferent polarities are reliably written in the adjacent two pixels.This provides a liquid crystal display panel as shown in FIG. 3 so thatpseudo inversion driving is performed.

[0155] The polarities of the signals applied to the image signal lines 2may be such that the negative and positive polarities alternate alongthe scan signal lines 3, as shown in (2) of FIG. 23.

[0156] In each of the embodiments, the polarities of the image signalvoltages impressed on the image signal lines 2 are inverted on a perframe basis such that ac voltages are impressed on pixels and the twosignal patterns shown in (1) and (2) of FIG. 23 are switched on a perframe basis. As a result, the image signal voltages written in the twopixels which are adjacent in the longitudinal or lateral direction ofthe liquid crystal display panel have different polarities and an acvoltage having a polarity inverted on a per frame basis is impressed oneach of the pixels. This enables dot inversion display free fromnon-uniform brightness and flicker which does not deteriorate under theinfluence of DC voltage.

[0157] A circuit configuration in which the polarity of each pixel isinverted on a per display period basis or on a perpredetermined-number-of-display-periods basis is well-known and easytechnique. The same shall apply to the case of pseudo dot inversion (inthe simplest manner, the positive and negative switches of each of theimage signal lines, the scan signal lines, and the like are switchedappropriately on a per display period basis). Therefore, the descriptionof the circuit and the like will be omitted. For reference purposes, acircuit for positive and negative impression in the eleventh and twelfthembodiments is conceptually shown in FIG. 24. Although information on animage is also inputted to a polarity switching portion on a per pixelbasis in practical use, it is not depicted for the prevention ofintricacy.

[0158] (Embodiment 12)

[0159] The present embodiment relates to a method for driving each ofthe liquid crystal display panels in the foregoing third and fourthembodiments.

[0160] In (3) and (4) of FIG. 23 is shown a circuit of the presentembodiment.

[0161] The polarities of the image signal voltages impressed on theimage signal lines 2 are alternately switched as shown in (3) of FIG. 23during a horizontal scan period during which a certain scan line isscanned, in (4) of FIG. 23 during another horizontal scan period duringwhich the subsequent scan line is scanned, and in (3) of FIG. 23 duringa still another horizontal scan period during which the subsequent scanline is scanned (the polarities of the image signal voltages areinverted on a per horizontal-scan-period basis such that positive andnegative polarities alternate). As a result, voltages of differentpolarities are written reliably in the adjacent two pixels in the liquidcrystal display panel as shown in FIG. 3 so that pseudo dot inversiondriving is performed.

[0162] (Embodiment 13)

[0163] The present embodiment relates to an improvement in color displaycharacteristics in pseudo dot inversion display. If the arrangement ofthree primary colors on a color display panel is in a mosaic pattern,the primary colors of red (R), green (G), and blue (B) are repeatedlyarranged in this order in oblique directions so that, if red is used asan example, lines in positive (+) display and lines in negative (−)display are arranged alternately. This causes a problem if the colordisplay panel is used by those particular with color or for professionalpurposes. In the arrangement in stripes, however, the positive andnegative displays are repeated on a per pixel basis in a longitudinal(or lateral) red stripe and the repetition of the positive and negativedisplays is shifted by one pixel position in an adjacent red stripedisposed three lines apart. This achieves more preferable red display.

[0164] The technology is shown in FIG. 25. In (1) of FIG. 25 is shownthe distribution of the positive and negative polarities of theindividual pixels in pseudo dot conversion. The technology is basicallythe same as shown in FIG. 3 so that ◯ represents the positive ornegative polarity and the polarity of each of the pixels is inverted ona per display period basis. In (2) of FIG. 25 is shown the placement ofthe positive and negative polarities of red pixels which are arranged ina mosaic pattern. In this case, the groups of red pixels of the positivepolarities and the groups of red pixels of the negative polarities arearranged alternately in oblique directions as shown on the right side of(2) of FIG. 25. Likewise, the case of longitudinal stripes is shown in(3) of FIG. 25.

[0165] (Embodiment 14)

[0166] The present embodiment relates to the case of liquid crystallogic elements.

[0167] In recent years, an optical logic element 67 for outputting, astransmitted light 66, the result of an arithmetic operation performedwith respect to incident light 65 has been developed, as shown in FIG.26. In an application to an optical computer, the optical logic elementis required to have high reliability and performance. In this case also,high reliability and performance satisfying the requirements has beenobtained by combining the technologies described in the foregoingembodiments.

[0168] Although the present invention has been described based on someof the embodiments thereof, it will be appreciated that the presentinvention is not limited thereto. The following arrangements are alsopossible.

[0169] (1) Other types of liquid crystal materials and semiconductormaterials may be used. For example, Si—C—Ge or Si—Ge may be used as asemiconductor material.

[0170] (2) The sizes of semiconductor elements and pixels are notlimited.

[0171] (3) So long as a liquid crystal and a TFT or diode are used, aliquid crystal shutter is used in a product or object other than aliquid crystal device or a liquid crystal optical logic element, such asgoggles, and a liquid crystal focusing mechanism is used in a camera.

[0172] (4) A pixel may have another configuration of another size, suchas a rectangle which is about 50 μm in size. A TFT may also have anotherconfiguration of another size, which is about 10 μm long in the channeldirection.

[0173] (5) The liquid crystal device may be of reflection type orreflection/transmission dual-purpose type.

INDUSTRIAL APPLICABILITY

[0174] As can be understood from the foregoing description, the presentinvention eliminates, in an active matrix liquid crystal display panelusing thin-film transistors as switching elements, a performancedifference between the thin-film transistors for individual pixels inthe panel which is produced under manufacturing constraints when pseudodot inversion driving is performed. This allows excellent images to bedisplayed on the liquid crystal display panel.

[0175] The present invention also contributes to more excellent colordisplay.

What is claimed is:
 1. A liquid crystal device having a plurality ofscan signal lines and a plurality of image signal lines providedorthogonally on a substrate and having thin-film transistors provided insections enclosed by the scan signal lines and the image signal lines,each of the thin-film transistors serving as a switching elementcorresponding to one of the sections and controlling transmission oflight by a semiconductor layer, the liquid crystal device usingpatterning to form the signal lines and the thin-film transistors,wherein: two of the thin-film transistors located between an adjacenttwo of the image signal lines having respective source electrodes areconnected to different image signal lines; and the respective gate,source, and drain electrodes of the two thin-film transistors arealignment-shift-compensated electrodes having configurations andstructures such that, even if an alignment shift occurs during theformation of the gate, source, and drain electrodes through thepatterning, at least one of a capacitance between the gate and drainelectrodes and a capacitance between the gate and source electrodes isconstant or varies equally in each of the two transistors.
 2. A liquidcrystal device having a plurality of scan signal lines and a pluralityof image signal lines provided orthogonally on a substrate and havingthin-film transistors each provided in sections enclosed by the scansignal lines and the image signal lines, each of the thin-filmtransistors serving as a switching element corresponding to one of thesections and controlling transmission of light by a semiconductor layer,the liquid crystal device using patterning to form the signal lines andthe thin-film transistors, wherein: two of the thin-film transistorslocated between an adjacent two of the scan signal lines havingrespective gate electrodes are connected to different scan signal lines;and the respective gate, source, and drain electrodes of the twothin-film transistors are alignment-shift-compensated electrodes havingconfigurations and structures such that, even if an alignment shiftoccurs during the formation of the gate, source, and drain electrodesthrough the patterning, at least one of a capacitance between the gateand drain electrodes and a capacitance between the gate and sourceelectrodes is constant or varies equally in each of the two transistors.3. The liquid crystal device of claim 1, wherein each of the two thinfilm transistors is an overlapping-area-compensated thin-film transistorformed as means for compensating for at least one of a variation in thecapacitance between the gate and drain electrodes and a variation in thecapacitance between the gate and source electrodes caused by thealignment shift such that at least one of a variation in an overlappingarea between the gate and drain electrodes and a variation in anoverlapping area between the gate and source electrodes responsive tothe alignment shift is constant or equal.
 4. The liquid crystal deviceof claim 2, wherein each of the two thin film transistors is anoverlapping-area-compensated thin-film transistor formed as means forcompensating for at least one of a variation in the capacitance betweenthe gate and drain electrodes and a variation in the capacitance betweenthe gate and source electrodes caused by the alignment shift such thatat least one of a variation in an overlapping area between the gate anddrain electrodes and a variation in an overlapping area between the gateand source electrodes responsive to the alignment shift is constant orequal.
 5. The liquid crystal device of claim 1, wherein each of the twothin film transistors is an overlapping-area-compensated thin-filmtransistor formed as means for compensating for at least one of avariation in the capacitance between the gate and drain electrodes and avariation in the capacitance between the gate and source electrodescaused by the alignment shift such that at least one of a variation inan overlapping area between the semiconductor layer and the drainelectrode and a variation in an overlapping area between thesemiconductor layer and the source electrode responsive to the alignmentshift is constant or equal.
 6. The liquid crystal device of claim 2,wherein each of the two thin film transistors is anoverlapping-area-compensated thin-film transistor formed as means forcompensating for at least one of a variation in the capacitance betweenthe gate and drain electrodes and a variation in the capacitance betweenthe gate and source electrodes caused by the alignment shift such thatat least one of a variation in an overlapping area between thesemiconductor layer and the drain electrode and a variation in anoverlapping area between the semiconductor layer and the sourceelectrode responsive to the alignment shift is constant or equal.
 7. Theliquid crystal device of claim 1, wherein each of the two thin filmtransistors is an overlapping-area-compensated thin-film transistorformed as means for compensating for at least one of a variation in thecapacitance between the gate and drain electrodes and a variation in thecapacitance between the gate and source electrodes caused by thealignment shift such that at least one of a variation in an overlappingarea between a channel protective film and the drain electrode and avariation in an overlapping area between the channel protective film andthe source electrode responsive to the alignment shift is constant orequal.
 8. The liquid crystal device of claim 2, each of the two thinfilm transistors is an overlapping-area-compensated thin-film transistorformed as means for compensating for at least one of a variation in thecapacitance between the gate and drain electrodes and a variation in thecapacitance between the gate and source electrodes caused by thealignment shift such that at least one of a variation in an overlappingarea between a channel protective film and the drain electrode and avariation in an overlapping area between the channel protective film andthe source electrode responsive to the alignment shift is constant orequal.
 9. The liquid crystal device of any one of claims 1, 3, 5, and 7,wherein, if the source and drain electrodes of the first one of the twothin-film transistors connected to the first one of the image signallines are S1 and D1 and the source and drain electrodes of the secondone of the two thin-film transistors connected to the second one of theimage signal lines are S2 and D2, the four electrodes are arranged alongthe image signal lines in the order of S1, D1, S2, and D2 or D1, S1, D2,and S2.
 10. The liquid crystal device of any one of claims 1, 3, 5, and7, wherein, if the source and drain electrodes of the first one of thetwo thin-film transistors connected to the first one of the image signallines are S1 and D1 and the source and drain electrodes of the secondone of the two thin-film transistors connected to the second one of theimage signal lines are S2 and D2, the four electrodes are arranged alongthe scan signal lines in the order of S1, D1, S2, and D2 or D1, S1, D2,and S2.
 11. The liquid crystal device of any one of claims 2, 4, 6, and8, wherein, if the source and drain electrodes of the first one of thetwo thin-film transistors connected to the first one of the scan signallines are S1 and D1 and the source and drain electrodes of the secondone of the two thin-film transistors connected to the second one of thescan signal lines are S2 and D2, the four electrodes are arranged alongthe scan signal lines in the order of S1, D1, S2, and D2 or D1, S1, D2,and S2.
 12. The liquid crystal device of any one of claims 2, 4, 6, and8, wherein, if the source and drain electrodes of the first one of thetwo thin-film transistors connected to the first one of the scan signallines are S1 and D1 and the source and drain electrodes of the secondone of the two thin-film transistors connected to the second one of thescan signal lines are S2 and D2, the four electrodes are arranged alongthe image signal lines in the order of S1, D1, S2, and D2 or D1, S1, D2,and S2.
 13. The liquid crystal device of any one of claims 1, 3, and 5,wherein each of the two thin-film transistors is such that the sourceelectrode or electrodes are larger in number than the drain electrode orelectrodes thereof or the drain electrode or electrodes are larger innumber than the source electrode or electrodes; the source and drainelectrodes are arranged alternately in parallel with the scan signallines; the source and drain electrodes have both ends extending off atleast one of the semiconductor layer and a channel protective film indirections along the scan signal lines when viewed from above an uppersurface of the substrate; and those ones of the electrodes which arelarger in number than the other electrode or electrodes include twolocated at both ends in directions along the image signal lines andextending off at least one of the semiconductor layer and the channelprotective film in directions opposite to the directions along the imagesignal lines when viewed from above the upper surface of the substrate.14. The liquid crystal device of any one of claims 2, 4, and 6, whereineach of the two thin-film transistors is such that the source electrodeor electrodes are larger in number than the drain electrode orelectrodes thereof or the drain electrode or electrodes are larger innumber than the source electrode or electrodes; the source and drainelectrodes are arranged alternately in parallel with the scan signallines; the source and drain electrodes have both ends extending off atleast one of the semiconductor layer and a channel protective film indirections along the scan signal lines when viewed from above an uppersurface of the substrate; and those ones of the electrodes which arelarger in number than the other electrode or electrodes include twolocated at both ends in directions along the image signal lines andextending off at least one of the semiconductor layer and the channelprotective film in directions opposite to the directions along the imagesignal lines when viewed from above the upper surface of the substrate.15. The liquid crystal device of claim 1, wherein each of the twothin-film transistors is such that the source electrodes and the drainelectrodes are a plurality of source electrodes and a plurality of drainelectrodes and are equal in number; the source and drain electrodes arearranged alternately in parallel with the scan signal lines; the sourceand drain electrodes have both ends extending off at least one of thesemiconductor layer and a channel protective film in directions alongthe scan signal lines when viewed from above an upper surface of thesubstrate; and those ones of the source and drain electrodes located atboth ends in directions along the image signal lines extend off at leastone of the semiconductor layer and the channel protective film indirections opposite to the directions along the image signal lines whenviewed from above the upper surface of the substrate.
 16. The liquidcrystal device of claim 1, wherein each of the two thin-film transistorsis such that the source electrodes and the drain electrodes are aplurality of source electrodes and a plurality of drain electrodes andare equal in number; the source and drain electrodes are arrangedalternately in parallel with the image signal lines; the source anddrain electrodes have both ends extending off at least one of thesemiconductor layer, a gate insulating film, and a channel protectivefilm in directions along the image signal lines; and those ones of thesource and drain electrodes located at both ends in directions along thescan signal lines extend off at least one of the semiconductor layer andthe channel protective film in directions opposite to the directionsalong the scan signal lines when viewed from above the upper surface ofthe substrate.
 17. The liquid crystal device of claim 2, wherein each ofthe two thin-film transistors is such that the source electrodes and thedrain electrodes are a plurality of source electrodes and a plurality ofdrain electrodes and are equal in number; the source and drainelectrodes are arranged alternately in parallel with the scan signallines; the source and drain electrodes have both ends extending off atleast one of the semiconductor layer and a channel protective film indirections along the scan signal lines when viewed from above an uppersurface of the substrate; and those ones of the source and drainelectrodes located at both ends in directions along the image signallines extend off at least one of the semiconductor layer, a gateinsulating film, and the channel protective film in directions oppositeto the directions along the scan signal lines when viewed from above theupper surface of the substrate.
 18. The liquid crystal device of claim2, wherein each of the two thin-film transistors is such that the sourceelectrodes and the drain electrodes are a plurality of source electrodesand a plurality of drain electrodes and are equal in number; the sourceand drain electrodes are arranged alternately in parallel with the imagesignal lines; the source and drain electrodes have both ends extendingoff at least one of the semiconductor layer and a channel protectivefilm in directions along the scan signal lines when viewed from above anupper surface of the substrate; and those ones of the source and drainelectrodes located at both ends in directions along the image signallines extend off at least one of the semiconductor layer and the channelprotective film in directions opposite to the directions along the scansignal lines when viewed from above the upper surface of the substrate.19. The liquid crystal device of claim 1, wherein the two thin-filmtransistors have the respective two drain electrodes each composed of athin-film semiconductor such that overlapping portions between the twodrain electrodes and the gate electrodes are formed in the samedirections relative to directions along the scan signal lines whenviewed from above an upper surface of the substrate.
 20. The liquidcrystal device of any one of claims 1, 3, 5, 7, 15, 16, and 19,comprising pseudo-dot-inversion implementing means for impressing imagesignal voltages of opposite polarities on the adjacent two image signallines.
 21. The liquid crystal device of claim 9, comprisingpseudo-dot-inversion implementing means for impressing image signalvoltages of opposite polarities on the adjacent two image signal lines.22. The liquid crystal device of claim 10, comprisingpseudo-dot-inversion implementing means for impressing image signalvoltages of opposite polarities on the adjacent two image signal lines.23. The liquid crystal device of claim 13, comprisingpseudo-dot-inversion implementing means for impressing image signalvoltages of opposite polarities on the adjacent two image signal lines.24. The liquid crystal device of claim 20, comprising frame-polarityinverting means for inverting the polarities of the image signalvoltages impressed on the individual image signal lines over an entireframe on a per predetermined-number-of-frames basis.
 25. The liquidcrystal device of claim 21, comprising frame polarity inverting meansfor inverting the polarities of the image signal voltages impressed onthe individual image signal lines over an entire frame on a perpredetermined-number-of-frames basis.
 26. The liquid crystal device ofclaim 22, comprising frame polarity inverting means for inverting thepolarities of the image signal voltages impressed on the individualimage signal lines over an entire frame on a perpredetermined-number-of-frames basis.
 27. The liquid crystal device ofclaim 23, comprising frame polarity inverting means for inverting thepolarities of the image signal voltages impressed on the individualimage signal lines over an entire frame on a perpredetermined-number-of-frames basis.
 28. The liquid crystal device ofany one of claims 2, 4, 6, 7, 8, and 18, comprising pseudo-dot-inversionimplementing means for impressing image signal voltages of the samepolarities on the image signal lines during the same scan period andinverting the polarities of the voltages on a perspecified-horizontal-scan-period basis.
 29. The liquid crystal device ofclaim 11, comprising pseudo-dot-inversion implementing means forimpressing image signal voltages of the same polarities on the imagesignal lines during the same scan period and inverting the polarities ofthe voltages on a per specified-horizontal-scan-period basis.
 30. Theliquid crystal device of claim 12, comprising pseudo-dot-inversionimplementing means for impressing image signal voltages of the samepolarities on the image signal lines during the same scan period andinverting the polarities of the voltages on a perspecified-horizontal-scan-period basis.
 31. The liquid crystal device ofclaim 14, comprising pseudo-dot-inversion implementing means forimpressing image signal voltages of the same polarities on the imagesignal lines during the same scan period and inverting the polarities ofthe voltages on a per specified-horizontal-scan-period basis.
 32. Theliquid crystal device of claim 28, comprising frame-polarity invertingmeans for inverting the polarities of the image signal voltagesimpressed on the thin-film transistors connected to the same scan signalline over an entire frame on a per predetermined-number-of-frames basis.33. The liquid crystal device of claim 29, comprising frame-polarityinverting means for inverting the polarities of the image signalvoltages impressed on the thin-film transistors connected to the samescan signal line over an entire frame on a perpredetermined-number-of-frames basis.
 34. The liquid crystal device ofclaim 30, comprising frame-polarity inverting means for inverting thepolarities of the image signal voltages impressed on the thin-filmtransistors connected to the same scan signal line over an entire frameon a per predetermined-number-of-frames basis.
 35. The liquid crystaldevice of claim 31, comprising frame-polarity inverting means forinverting the polarities of the image signal voltages impressed on thethin-film transistors connected to the same scan signal line over anentire frame on a per predetermined-number-of-frames basis.
 36. Theliquid crystal device of claim 20, wherein the device is a color liquidcrystal display device having pixels in primary colors arranged instripes.
 37. The liquid crystal device of claim 24, wherein the deviceis a color liquid crystal display device having pixels in primary colorsarranged in stripes.
 38. The liquid crystal device of claim 28, whereinthe device is a color liquid crystal display device having pixels inprimary colors arranged in stripes.
 39. The liquid crystal device ofclaim 32, wherein the device is a color liquid crystal display devicehaving pixels in primary colors arranged in stripes.
 40. A liquidcrystal device having scan signal lines, diodes, and pixel electrodesprovided on one substrate, having image signal lines provided on theother substrate, and having a liquid crystal layer sandwiched betweenthe two substrates, wherein: two of the diode elements located betweenan adjacent two of the scan signal lines having respective gateelectrodes are connected to different scan signal lines; and each of thediodes is an alignment-shift-compensated diode having a configurationand a structure such that, even if an alignment shift occurs duringformation of the electrodes through patterning, a capacitance isconstant or varies equally in each of the two diodes.
 41. The liquidcrystal device of claim 40, wherein the device is a color liquid crystaldisplay device having pixels in primary colors arranged in stripes.